Hoodfar, an anthropology professor, was visiting Iran to see family and do academic research when she was arrested by the counter-intelligence unit of the Iranian Revolutionary Guards, which seized her laptop and passport.

She was released on bail but was arrested again this past Monday.

Since then, her extended family has been unable to make contact with her, and they say they're worried about her fragile health.

Hoodfar's former students are also expressing shock over what's happened.

Kathryn Jezer-Morton took a graduate class with her in 2014.

"Just the thought that she would be in any kind of stressful situation was really shocking to me, she's just a lovely person and a lovely professor," she said.